1. Field of the Invention
The present invention relates to wireless communication and, more particularly, to an apparatus and method for configuring radio connection in a multiple component carrier system.
2. Related Art
Wireless communication systems are widely deployed in order to provide various kinds of communication services, such as voice and data. In general, the wireless communication systems are multiple access systems which can share available system resources (e.g., bandwidths and transmission power) and support communication with multiple users. The multiple access systems can include, for example, a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.
In a common wireless communication system, although the bandwidth of uplink and the bandwidth of downlink are differently set up, only one carrier is taken into consideration. Even in 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), the number of carriers constituting uplink and downlink is 1, and the bandwidth of uplink and the bandwidth of downlink bandwidth are in general symmetrical to each other on the basis of a single carrier. However, it is not easy to allocate a large frequency bandwidth except some regions in the world. Accordingly, in order to efficiently use small sliced bands, a spectrum aggregation technique for producing the same effect as that a logically large band is used by binding a plurality of physically non-continuous bands in the frequency domain is being developed. The spectrum aggregation technique includes, for example, a technique in which 3GPP LTE is configured to support the system bandwidth of 100 MHz using multiple carriers although it supports the bandwidth of a maximum of 20 MHz and a technique in which an asymmetrical bandwidth is allocated between uplink and downlink.
Meanwhile, a User Equipment (UE) can be in a Radio Resource Control (RRC) connected mode or an RRC idle mode. When the UE is in the RRC connected mode, the UE and a Base Station (BS) have their radio links connected to each other. When the UE is in the RRC idle mode, the UE can connect a radio link to the BS by sending an RRC connection request message to the BS at any time.
In a multiple component carrier system, however, whether an RRC connection request message will be sent through which component carrier has not yet been determined. Further, in the case in which a plurality of user equipments perform an RRC connection request through only a specific component carrier having a good channel state, overhead can occur because of excessive uplink transmission through the specific component carrier. Accordingly, there is a need for an apparatus and method for configuring radio connection by properly distributing component carriers used for the radio connection.